In optics, Wadsworth's constant-deviation prism-mirror system (or Wadsworth constant deviation mounting) is a method to arrange a prism or diffraction grating and a mirror on a turntable to ensure that rays of light emerge in a fixed direction.
[1] Typically, light entering via a slit is directed into the prism by a lens.
A particular wavelength can be chosen for analysis by setting the angle of the prism, and hence the part of the spectrum that exits by a mirror and lens combination.
[3] It is considered a "classic" prism configuration being versatile on its own or in combination with many other configuration and instrumentation combinations.
[4] Among many other applications, Wadsworth constant deviation mountings have been used to study light emissions from excited metal atoms,[5] and to study the light needs of plants in future space missions.